Treatment optimization with concurrent SBRT and intracavitary brachytherapy for locally advanced cervical cancer.

Bin Wan,C‐M Ma,Jinyi Lang,Pei Wang

doi:10.1120/jacmp.v17i1.5610

Abstract

This work is aimed at investigating treatment planning strategies to optimally combine stereotactic body radiation therapy (SBRT) with intracavitary brachytherapy (ICBT) for the treatment of locally advanced cervical cancer. Forty patients (stage IIB – IIIB) previously treated with combined SBRT and ICBT were randomly selected for this retrospective study. All patients were CT‐ and MR‐scanned with a ring applicator in situ. HR‐CTV and OARs were contoured according to fused CT and MR images. Several ICBT plans were generated for each patient based on different dose prescription points, and then a matching SBRT plan was generated for each ICBT plan. The dose distribution of each composite plan was analyzed with a focus on the doses received by 90% and 100% of the target volume (D90 and D100), the target volume receiving 100% of the prescription dose (V100%), and the doses received by 2 cc and 40% of the OARs (D2cc and D40). As the distance, d, between the prescription point and the tandem varied within 1.0 and 1.9 cm, the D90, D100 and V100% for the target, as well as D2cc and D40 for the bladder and rectum approached their optimal values for d value between 1.0 and 1.4 cm. When designing a combined ICBT+SBRT plan, one should measure the size of the cervix and set the prescription isodose line 1.0 to 1.4 cm away from the tandem for the ICBT plan first and then optimize the SBRT plan based on the ICBT dose distribution to achieve the best target coverage and critical structures sparing.PACS number: 87.53.jw; 87.55.D‐

Highlights

71 Wan et al.: Combined stereotactic body radiation therapy (SBRT) and intracavitary brachytherapy for cervical cancer associated with placing needles in a desirable configuration.(2,3) On the other hand, when the tumor has a close relationship with an organ at risk (OAR), it can be difficult to achieve adequate tumor coverage by ICBT + SBRT due to dose constraints by the surrounding OARs.(1) According to these investigations, whether ICBT + IS or ICBT + SBRT should be used for a particular patient depends on the size/shape of the cervix/tumor target and/or the relationship between the treatment volume and nearby OARs
Plan evaluation In order to evaluate the quality of each plan generated, we compared all plans with different d values for each patient based on the following parameters: the dose values received by 90% of the target volume (D90), the dose received by 100% of the target volume (D100), the volume of the HR-CTV receiving 100% of the prescription dose (V100%), and the maximum doses received by 2 cc and 40% of the OARs (D2 cc and D40)
A large number of test plans were generated to determine the optimal conditions for the two treatment modalities to form a perfect match that will result in optimal dosimetric parameters for the combined ICBT + SBRT treatments

Summary

Introduction

71 Wan et al.: Combined SBRT and intracavitary brachytherapy for cervical cancer associated with placing needles in a desirable configuration.(2,3) On the other hand, when the tumor has a close relationship with an organ at risk (OAR), it can be difficult to achieve adequate tumor coverage by ICBT + SBRT due to dose constraints by the surrounding OARs.(1) According to these investigations, whether ICBT + IS or ICBT + SBRT should be used for a particular patient depends on the size/shape of the cervix/tumor target and/or the relationship between the treatment volume and nearby OARs.Dimopoulos et al(2) and Kirisits et al(3) have investigated the combination of ICBT + IS extensively. The round-point needle is designed to minimize tissue damage and improve ease in implantation. This applicator is designed to expand the target area without being limited by the OARs. the patients who accept the ICBT + IS treatment will have to endure a long treatment procedure, 5 to 8 hours from the implantation of needles to the treatment delivery,(3) which is a challenge for the nursing staff

Methods

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Discussion

Conclusion